The need to define the events of tumor-host interactions in modern immunological terms is apparent. By using autochthonous or transplanted syngeneic tumors in mice (including spontaneous mammary tumors and chemically induced lung adenocarcinomas) we will attempt to define: the dynamics of development of immunity after immunization; the dynamics of development of concomitant immunity in the tumor bearing host, the cell types involved in the response and regulation of such response especially T-dependent ones; the antibodies produced during such responses and the significance of the different tumor-associated antigens in triggering "selectively" humoral or cellular immunity and amplifying suppressive control mechanisms. The mammary tumor in mice has some intrinsic advantages for the study of such events since some of the viral antigens are relatively well-defined biochemical entities. Both by selective stimulation or inhibition in vivo and in vitro of the immune lymphoid cells we will be able to define the significance of such antigens as stimuli for the host immune response. The correlation of the in vitro technology with in vivo assays will emphasize the biological significance of such events. The information generated by such approach could be used for a rational investigation of specific and non-specific immune potentiation.